The SL 218 A is a professional active subwoofer designed to complement existing PA systems in the sub-bass range. Thanks to its integrated active electronics, adding the SL 218 A to an existing system is as easy as can be, since no extra amp racks or crossovers, etc., are needed. The SL 218 A is equipped with two direct-radiating 18" speakers in separate chambers, each powered by a state-of-the-art PWM power amplifier whose total capacity is 2.000 watts RMS. To facilitate optimal integration of the SL 218 A in an existing PA system, the unit includes gain control, phase reversal switch (0° - 180°) and a 12-dBper- octave crossover adjustable between 60 Hz and 100 Hz. If the SL 218 A is being operated with an HK AUDIO® Digital Field Controller (DFC) or some other digital controller or external crossover, you can switch the subwoofer's internal crossover completely out of the circuit using the integral bypass switch. When the SL 218 A is used within a DFC-controlled sound reinforcement system, it is recommended that a separate DFC be deployed for the SL 218 A. This allows it to be operated via remote control as one component within a DFC network from a single PC or notebook computer running the HK AUDIO® DFC software. The SL 218 A is equipped with a lockable Neutrik Powercon mains power connector and four 100-mm (4") wheels. The appropriate power cable for local voltage and a rugged panel to protect the baffle during transport are included.